Process and composition for electroplating copper



United States Patent Office 3,084,112 Patented Apr. 2, 1963 3,084,112 PROCESS AND COMPOSITION FOR ELECTRO- PLATING COPPER Peter Leenders and Hans G. Creutz, Detroit, Mich., assignors to Allied Research Products, Incorporated, Baltimore, Md., a corporation of Maryland No Drawing. Filed July 29, 1960, Ser. No. 46,102 7 Claims. (Cl. 204-52) The present invention relates to electrodepositing copper from an aqueous alkaline cyanide copper plating bath and to a composition for improving such baths.

It has previously been proposed to employ butynediol 1,4 and similar acetylenic compounds to produce a bright copper electroplate from an aqueous alkaline cyanide copper plating bath as in Foulke Patent No. 2,881,121 and Schering German Patent No. 924,490. Such procedures have the disadvantage that there is a tendency to stain copper electroplate. Additionally, there are undesirable effects caused by sulfur which is normally present as an impurity in the cyanide bath. Furthermore, the electroplated copper cannot be readily buffed.

It is an object of this invention to eliminate the disadvantages normally associated with the use of butynediol 1,4 and the like in alkaline cyanide copper plating baths to form a bright deposit of copper.

Another object is to eliminate the staining normally present in such baths.

An additional object is to obtain a soft or ductile deposit of copper from an alkaline cyanide copper plating bath which can be readily buffed.

A further object is to raise the anode efiiciency in alkaline cyanide copper plating baths containing butynediol 1,4.

Yet another object is to plate copper from an alkaline cyanide bath containing chromium, zinc or iron salts.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by Way'of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description,

It has now been found that these objects can be attained by incorporating in the alkaline cyanide Copper plating bath a mixture of certain acetylenic alcohols and a sugar heptonic acid.

The preferred acetylenic alcohol is Z-butynediol 1,4 and it has been found to be far superior to any other acetylenic alcohol tested. Other acetylenic alcohols which can be employed include 3-methyl-l-butyne-3-ol, 3-methyl-lpentyne-3-ol, l-ethynylcyclohexanol, phenyl-propynol and 3-phenyl-l-butyne-3wl.

The following acetylenic alcohols have proven to be unsatisfactory: propargyl alcohol, methyl butynol-ethylene oxide adduct, 2-methyl-4-chloro-3-butyne-2-ol, dimethyl hexynediol, dimethylhexynediol-ethylene oxide adduct, dimethyloctynediol and phenylbutynol.

-As the sugar heptonic acid there can be employed ot-heptagluconic acid, fi-heptagluconic acid, a-manno-heptonic acid, u-galaheptonic acid, fi-galaheptonic acid, fructoheptonic acid. and rhamnoheptonic acid. -Both the d and 1 forms of the sugar acids can be employed. The sugar acids are normally employed as their alkali metal salts, e.g. sodium heptagluconate and potassium heptagluconate. Even if the free sugar acid is employed it is converted to the alkali metal salt in the cyanide bath.

The preferred sugar acid material is a mixture of potassium a d-heptagluconate and potassium ,8-d-heptagluconate made in conventional fashion by condensing d-glucose with potassium cyanide and then hydrolyzing the glucose cyanohydria with aqueous potassium hydroxide. This material is identified as potassium heptagluconate in the examples. In place of the potassium heptagluconate sodium heptagluconate can be employed with similar effect.

Normally, the Z-butynediol 1,4 is employed in an amount of 1 to 5 parts with to 500 parts of the potassium heptagluconate or equivalent material.

The alkali cyanide copper plating bath can be that in standard operation other than for the above additive. Such baths usually contain from 20 to 75 grams per liter of copper and. 45 to grams per liter of an alkali metal cyanide. While the 2-lbutynediol 1,4 can 'be employed in an amount of 0.01 to 200' millimoles per liter preferably it is employed in an amount of 1 to 100 As a result of the present invention bright copper electrodeposits are obtained from alkaline-cyanide copper solutions on conventional base metals such as iron, steel, nickel, zinc, lead, copperand alloys, e.g. brass. With steel or zinc preferably the base metal is given an initial ghitrtil flash of copper from a low efliciency cyanide copper In the specification and claims, all proportions are by weight unless otherwise indicated,

In Examples 1-3, the plating operations were carried out in a 280 ml. Hull test all having brass cathodes at a temperature of F.

Wetting agents can be added such as lauryl oxyethylsulfate, nonylphenol-polyethylene oxidenitrite, sodium toluene .sulfonate, potassium naphthalene-bis-methylene sulfonate. V

In the examples, bright deposits were obtained over a current density range of 1 to 100 amperes/sq. ft- There was a noticeable increase in anode efliciency over the use of formulations omitting the heptagluconate. No staining of the plated copper was noted. The deposit of copper obtained on the electrode Was ductile and readily buffed.

Example 1 Material: Proportions (grams/liter) CuCN 70 KCN s 12o KOH 23.5 Triethanolamine 20 Potassium heptagluconate... 20 Phenylpropynol e 0.2 2-butynediol 1,4 0.3 Lauryl alcohol ether sulfate 0.05 Potassium thiocyanate l0 Example 2 Material: Proportions (grams/liter) CuCN 65 KCN 106 KOH 23.5 Triethylenetetramine 20 Rochelle salt 25 Potassium heptagluconate Ethynyl cyclohexanol 0.5 Z-butynediol 1,4 0.2 Ammonium thiocyanate 1 Nonylphenol-ethyleneoxide polyethylene nitrite 0.05

Example 3 Material: Proportions (grams/liter) CuCN 60 KCN 100 KOH 15 Rochelle salt Potassium hcptagluconate 20 Sodium ethylenediamine tetraacetate 5 Z-butynediol 1,4 0.5 Sodium thiocyanate 1 Thallous gluconate 0.01

Ethomeen S (ethylene oxide adduct of mixed stearyl amine, palmityl amine and oleyl amine) 0.05

Example 4 A suitable aqueous formulation for adding to alkaline copper cyanide plating baths is as follows:

Pounds Potassium heptagluconate 750 Ethylenediamine tetraacetic acid 84 Triethanola mine 420 Z-butynediol 105 Water, sufficient to make 500 gallons.

In the following examples utilizing 21 Hull cell with a copper anode and a brass cathode, comparisons were made between (a) no additive, (b) Z-butynediol 1,4 or potassium heptagluconate additive and (c) Z-butynediol 1,4 and potassium heptagluconate additive.

Example 5 Stock plating solution: Oz./ Gal. Copper cyanide 10 Sodium cyanide 13 Sodium hydroxide 3 Test panels were treated with the stock solution containing the following additives: (a) No additive.

(b) 2-butynediol1,4 grams/liter 0.2

(c) Z-butynediol 1,4 do 0.2

and 1 Potassium heptagluconate oz/gal.-- 3

The following results were observed:

('a) The anode developed a rather heavy brown film. The cathode was dull over the entire 2 amp. test panel.

(b) The anode developed a brown film. The cathode was a bright reflecting plate between 10 and 40 amp. sq. ft., was stained at less than 10 amp/sq. ft. and was dull at greater than 40 amp./ sq. ft.

(0) The anode was clear. The cathode was a bright reflecting plate between 1 and amp/sq. ft., there was less staining atless than 10 amp/sq. ft. than in (b) and was dull at greater than 50 amp/sq. ft.

Example 6 Stock plating solution: Oz./gal. Copper cyanide 10 Sodium cyanide 13 Potassium hydroxide 3 Test panels were treated with the stock solution containing the following additives: (a) No additive.

(b) Potassium heptagluconate oz./gal. 5

(c) Potassium heptagluconate do 5 and 2-butynediol 1,4 gm./liter 0.01

The following results were observed:

(a) The anode developed a light brown film. The cathode was bright at less than 3 amp/sq. ft., semi-bright and heavily stained from 3 to 20 amp./ sq. ft., bright-semibright from 20 to 50 amp./ sq. ft. and was dull at greater than 50 amp/sq. ft.

(b) The anode was clear. The cathode had the same brightness as in test (a) but with diminished staining.

(c) The anode was clear. The brightness of the cathode was good without staining from 1 to amp./ sq. ft. with a light haze at 5 to 20 amp/sq. ft.

Example 7 Stock plating solution: Oz./ gal. Copper cyanide 10 Potassium cyanide 10 Potassium hydroxide 3 Test panels were treated with the stock solution containing the following additives:

(a) No additive (b) Z-butynediol 1,4 "gm/liter" 0.3

(c) 2-butynediol1,4 do 0.3

and

Potassium heptagluconate oz./gal 2 The following results were observed:

(a) The anode developed a light brown film. The cathode was semi-bright from 1 to 10 amp/sq. ft. and from 40 to 90 amp/sq. ft. with a light dull band from 10 to 40 amp/sq. ft.

(b) The anode developed a light brown film. The cathode had a hazy dullness from 1 to 10 amp/sq. ft. and was semi-bright from 10 to amp/sq. ft. The dull band was eliminated but there was heavy staining above 10 amp/sq. ft.

(c) The anode was clear. The cathode had a uniform hazy-bright plate from 10 to 100 amp/sq. ft. and was heavy-dull below 10 amp/sq. ft. The staining was eliminated.

What is claimed is:

1. An aqueous composition for use in an alkaline cyanide copper plating bath comprising an acetylenic alcohol of the group consisting of Z-butynediol 1,4, 3- methyl-1-butyne-3-ol, 3-methyl-1-pentyne-3-o1, l-ethynylcyclo-hexanol, phenylpropynol and 3-phenyl-1-butyne-3- 01 in an amount effective to provide from 0.01 to 200 millimoles of said alcohol per liter of said bath and a sugan heptonic acid in an amount effective to reduce staining of the plate by said bath.

2. An aqueous composition for use in an alkaline cyanide copper plating bath comprising Z-butynediol 1,4 in an amount effective to provide from 0.01 to 200 millimoles of said butynediol per liter of said bath and an alkali metal heptagluconate in an amount effective to reduce staining of the plate by said bath.

3. An aqueous composition according to claim 2 wherein the butynediol and heptagluconate are present in the ratio of from 1 to 5 parts butynediol with 100 to 500 parts heptagluconate.

4. An aqueous composition according to claim 2 wherein the heptagluconate is a member of the group consisting of sodium heptagluconate and potassium heptagluconate.

5. A process for producing a bright copper electroplate which comprises electroplating copper from an aqueous alkaline cyanide copper plating bath containing a sugar heptonic acid and from 0.01 to 200 millimoles per liter of an acetylenic alcohol of the group consisting of Z-butynediol 1,4, 3-methyl-1-butyne-3-ol, 3-rnethyl- 1-pentyne-3-ol, l-ethynylcy-clohexanol, phenylpropynol and 3'phenyl-1-butyne-3-ol, said acid being present in an amount effective to reduce staining of the electroplate by said alcohol.

6 A process 'for producing a bright copper electroplate which comprises electroplating copper from an aqueous alkaline cyanide copper plating bath contain ing a heptagluconate of the group consisting of sodium 10 heptagluconate and potassium heptagluconate and from 0.01 to 200 millimoles per liter of Z-butynediol 1,4, said heptagluconate being present in an amount effective to reduce staining of the electroplate by said 2-butynediol 1,4.

7. A process according to claim 6 wherein the heptagl-uconate is present in an amount of 10 to 150 grams/ liter and the butynediol is present in an amount of 0.1 to 10 grams/liter.

References Cited in the file of this patent UNITED STATES PATENTS 694,658 Meurant Mar. 4, 1902 2,443,600 Chester June 2, 1948 2,881,122 Foul ke Apr. 7, 1959 OTHER REFERENCES Fieser et al.: Organic Chemistry, Reinhold Pub. Corp.,

15 1956, pages 350-351. 

1. AN AQUEOUS COMPOSITION FOR USE IN AN ALKALINE CYANIDE COPPER PLATING BATH COMPRISING AN ACETYLENIC ALCOHOL OF THE GROUP CONSISTING OF 2-BUTYNEDIOL 1,4, 3METHYL-1-BUTYNE-3-OL, 3-METHYL-1-PENTYNE-3-OL, 1-ETHYNYLCYCLO-HEXANOL, PHENYLPROPYNOL AND 3-PHENYL-1-BUTYNE-3OL IN AN AMOUNT EFFECTIVE TO PROVIDE FROM 0.01 TO 200 MILLIMOLES OF SAID ALCOHOL PER LITER OF SAID BATH AND A SUGAR HEPTONIC ACID IN AN AMOUNT EFFECTIVE TO REDUCE STAINING OF THE PLATE BY SAID BATH. 